Hexakosioihexekontahexaphobia is a fear which originates in the belief that the Biblical verse, Revelation 13:18, indicates that the number 666 is linked to Satan or the Anti-Christ. Outside the Christian faith, the phobia has been further popularized as a leitmotif in various horror films. Hexakosioihexekontahexaphobes avoid things related to the number 666, such as a building in which the number is prominently displayed. Rarer is trying to avoid the number as it relates to other numbers. For example, the fraction two-thirds has a repeating decimal of .666. (Note that in base 12, two-thirds is 0.8, and 0.666 is the fraction 6/11.) A severe hexakosioihexekontahexaphobic may avoid this as well as 5/3, 8/3, 11/3, etc. People with this phobia consider it bad luck to get 3 sixes in a hand of poker, even though this is usually quite a good hand. (From Bits and Pieces)